[PATCH] SysRq-X: show blocked tasks

Add SysRq-X support: show blocked (TASK_UNINTERRUPTIBLE) tasks only.

Useful for debugging IO stalls.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 31 insertions, 5 deletions

diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index c64f5bcff947..05810c8d20bc 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -182,6 +182,18 @@ static struct sysrq_key_op sysrq_showstate_op = {
         .enable_mask    = SYSRQ_ENABLE_DUMP,
 };
 
+static void sysrq_handle_showstate_blocked(int key, struct tty_struct *tty)
+{
+        show_state_filter(TASK_UNINTERRUPTIBLE);
+}
+static struct sysrq_key_op sysrq_showstate_blocked_op = {
+        .handler        = sysrq_handle_showstate_blocked,
+        .help_msg       = "showBlockedTasks",
+        .action_msg     = "Show Blocked State",
+        .enable_mask    = SYSRQ_ENABLE_DUMP,
+};
+
+
 static void sysrq_handle_showmem(int key, struct tty_struct *tty)
 {
         show_mem();
@@ -304,7 +316,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
         /* May be assigned at init time by SMP VOYAGER */
         NULL,                           /* v */
         NULL,                           /* w */
-        NULL,                           /* x */
+        &sysrq_showstate_blocked_op,    /* x */
         NULL,                           /* y */
         NULL                            /* z */
 };
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 837a012f573c..0a90cefb0b0d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -194,7 +194,16 @@ extern void init_idle(struct task_struct *idle, int cpu);
 
 extern cpumask_t nohz_cpu_mask;
 
-extern void show_state(void);
+/*
+ * Only dump TASK_* tasks. (-1 for all tasks)
+ */
+extern void show_state_filter(unsigned long state_filter);
+
+static inline void show_state(void)
+{
+        show_state_filter(-1);
+}
+
 extern void show_regs(struct pt_regs *);
 
 /*
diff --git a/kernel/sched.c b/kernel/sched.c
index 12fdbef1d9bf..1848e280504d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4804,7 +4804,7 @@ static void show_task(struct task_struct *p)
                 show_stack(p, NULL);
 }
 
-void show_state(void)
+void show_state_filter(unsigned long state_filter)
 {
         struct task_struct *g, *p;
 
@@ -4824,11 +4824,16 @@ void show_state(void)
                  * console might take alot of time:
                  */
                 touch_nmi_watchdog();
-                show_task(p);
+                if (p->state & state_filter)
+                        show_task(p);
         } while_each_thread(g, p);
 
         read_unlock(&tasklist_lock);
-        debug_show_all_locks();
+        /*
+         * Only show locks if all tasks are dumped:
+         */
+        if (state_filter == -1)
+                debug_show_all_locks();
 }
 
 /**